the three weeks of the experiment the large drills actively drilled and fed on the 

 young oysters and the smaller drills were active but killed very few oysters pre- 

 sumably because the oysters were too large to be effectively drilled by them . In 

 the entire experiment only one small drill (in the experimental aquaria) did not 

 survive . 



Destruction of Drills and Egg Cases 



A wide variety of methods for the destruction of drills and their egg cases 

 in situ on the bottom "and after capture appear in scattered published and unpublished 

 articles. These take the form of untried suggestions, or procedures tested with 

 different degrees of completeness. Some of these methods are cited here only for 

 their historical interest; others have merit in theory but are implausible economical- 

 ly and practicably, or both; and some methods, after research or after extended 

 research and large scale testing, may result in wide application. 



Desiccation 



All stages of Urosalpinx within the egg case may be killed by exposure on 

 land for three or four days (Galtsoff et al . , 1937). The duration of exposure 

 necessary to destroy adults is not known. It would be useful to know the lethal 

 exposure time for drills of varying size in the shade and in the sun and at varying 

 depths in bottom trash dredged with the drills over a wide range of atmospheric 

 temperatures . 



Heat 

 Hot water 



Galtsoff et al. (1937) suggest that drills and egg cases collected during the 

 most vigorous part of the spawning season on such devices as shells in wire bags, 

 old tin cans, and on similar materials, be destroyed by dipping the collectors in 

 boiling water for 10 to 15 seconds . This immediately kills the drills and young 

 and permits immediate replacement of the collectors on the beds There is great 

 need for some means of destroying drills which pass through the- vibrating screens 

 of hydraulic suction dredges usually in company with large quantities of fine trash 

 and sediments . It is possible that hot water or steam may some day be employed 

 for this purpose . The problem is complicated, however, by the voluminous 

 quantities of trash and sediment which accompany the drills and which quickly 

 dissipate the heat necessary to effect destruction of the drills. To date the mech- 

 anical aspects of the problem remain unsolved. The potential effectiveness and 

 mexpensiveness of the method should encourage eventual practical solution. 



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